1. Field of the Invention
The invention relates generally to seismic energy vibrators and, more particularly, but not by way of limitation, it relates to an improved shear wave vibrator assembly for obtaining greater efficiency of energy input to an earth medium.
2. Description of the Prior Art
The prior art includes several types of vibrator support structures and earth-coupling structures which are the forerunner of the present invention. One teaching of particular interest is the U.S. Pat. No. 3,159,232 in the name of Delbert Fair and entitled "Shear Wave Transducer" which dealt with a shear wave vibrator assembly as rigidly supported by a single base plate, opposite sides of which included one or more pyramidal earth-coupling cleat structures of absolute symmetry and equi-angular character. The cleat structures in this invention were necessarily formed as an integral part of the base plate in order to assure the necessary positive coupling therebetween, an important consideration in coupling seismic energy into the earth's surface. Still other attempts are providing optimum coupling of shear wave energy into the earth's surface have taken the form of lateral cleating devices; see U.S. Pat. No. 3,372,770, in the name of Clynch, which teaches hydraulically driven lateral braces operative with the vibrational transducer to maintain the energy coupling base plate in positive contact with the earth throughout a vibrational sequence. In each case, the prior art attempts have fallen short of the prescribed mark due to the fact that the many different types of terrain will require a different form of coupling structure to best achieve seismic energy input to the earth.